It’s the future. No one really knows when, but it’s not so distant - everything looks pretty much the same as it did when we last saw it. The buildings, the subway stations, the billboards and the railway lines, they’re all there, except they’re now overgrown, hollowed out, and a little decrepit. There are no cars or buses, no pedestrians, oh and did I mention there are no humans? There are no humans. But there sure are a lot of pets, and some of them are wearing baseball caps.
In the 2011 video game, Tokyo Jungle, we learn that mankind ceased to be shortly after some Japanese physics professor received an anonymous email from the year 2215. Yes, an email from 200 years in the future:
“Some group sent me a really strange email today. They claim to be from the future, and as proof of that, they attached research data on my field of study 200 years from now. It must be spam and the attachment is probably a virus.”
Sounds sensible. Good job, professor. Nigerian royalty have now added you to their ‘Avoid: has basic knowledge of the Internet’ list.
Oh, but wait.
“Still, if I had research results from 200 years in the future, it would reduce the possibility of our budget being cut.”
Well, okay. I guess that’s one way of looking at it.
Long story short, humans 200 years from now want the professor to build a time machine to save them from themselves and something something... electromagnetic waves, the animals go crazy, dinosaurs appear as if from no where, humans start to disappear and/or die off - it’s not really clear. There’s a lone robotic dog with ambiguous motivations.
But the key point here is that these electromagnetic waves have made all the animals - pets, wildlife, zoo exotics, extinct giant moa birds - nuts. They now fight to survive, porcupines, beagles, ally cats and bears alike, with a ferocity like nothing we’ve ever seen before. They eat each other and breed like crazy, until their children, or their children’s children’s children end up in the wrong part of town and get mowed down by a pack of Dilophosauruses.
Life in post-apocalyptic Tokyo is a rough, but you know who would probably get along okay in it? The Norwegian lemming (Lemmus lemmus). Because look at this guy go:
He doesn’t even need electromagnetic waves to make him fierce, he does all of that on his own. And he’ll do it even from a distance of several metres away, instead of quietly scurrying away from a predator like a regular rodent. But why? He doesn't exactly have the skills to back up all that aggression.
And what about those beautiful colours? The reddish brown along his back, the yellow flanks and white breast, the contrasting chin and cheeks that break up that large black patch on his head, neck and shoulders. While some researchers have suggested these colours offer the Norwegian lemming a form of camouflage, they’re not exactly doing them any favours during the winter months, when much of their habitat is covered in clean, white snow.
So what is the deal with the Norwegian lemming? Zoologist Malte Andersson from the University of Gothenburg in Sweden has been investigating whether the species' pugnacious display actually works as an effective defence mechanism for the Norwegian lemming. Perhaps, he thought, all this conspicuousness in such a small animal could be an unusual example of aposematism - a signal, typically in the form of bright colouration, to warn predators that a creature is dangerous or unpalatable. This kind of defence is common in insects, frogs, snakes, and some sea creatures, but quite rare in mammals.
Throughout June and July in 2011, Andersson went out into the low alpine plains on the Flatruet plateau in Sweden to hunt Norwegian lemmings. Walking 10 to 15 kilometres every day, he would take note of the behaviour of a lemming as he spotted it and drew near. He did the same with brown lemmings (Lemmus trimucronatus) to see if the behaviour was shared across the species, or unique to Norwegian lemmings.
Reporting in the current edition of Behavioral Ecology and Sociobiology, Andersson says of the 110 encounters with Norwegian lemmings, 36 of them involved aggressive calling noises, and the distance between himself and the lemmings was what set them off. When they were surprised at a distance 5 metres or less, most of the lemmings called (or yelled, really), and they’d continue to call as they fled to a burrow or some nearby vegetation. But with 10 metres or more between them, the lemmings would silently scoot.
Of the 39 brown lemmings Andersson encountered, just one made defensive alarm calls - but only because it was being chased for capture. Which is something anyone would do if they're being chased for capture. Most of the brown lemmings were vocal and bitey only once they were being handled.
Andersson also wanted to figure out if the Norwegian lemming colouring was meant to be conspicuous, or if it did indeed offer some form camouflage. So he sent a bunch of people out into Norwegian lemming habitat and asked them to spot as many as they could, plus as many voles as they could in the same area. Voles have a much more subtle colouring, so it stood to reason that if the spotters found around the same amount of voles and Norwegian lemmings, this meant the bright lemming colours were actually suited to blending in to their environment. But if they found more lemmings than voles, then this would indicate their colouring gave them away. Andersson reports that his team was able to spot, on average, 61 percent of the Norwegian lemmings in the area, and just 43 percent of the voles. So it's unlikely that the colouring of the Norwegian lemming exists to lower their conspicuousness.
And then you have to consider that the human spotters have got nothing on the Norwegian lemmings’ avian predators, as Andersson explains in the paper:
"Humans have less advanced, trichromatic colour vision than tetrachromatic birds, which also see UV. Avian predators are therefore likely to see the differences in colouration between lemmings and voles perceived by humans, plus any differences in UV. The detectability test is therefore probably conservative in this respect, underestimating the colour differences perceived by avian predators between Norwegian lemmings and grey-sided voles.”
Perhaps, Andersson says, the colouring works in partnership with the aggressive calling behaviour. At close range, this brightly coloured lemming is going to be spotted, regardless of how little or much noise it makes, so maybe it evolved to yip like a post-apocalyptic Pomeranian when faced with a predator, because together with the colouration, this provides a convincing display of aposematism:
“An aposematic signal must be discriminable and memorable, but not necessarily conspicuous. The calls and contrasting yellow, white and black colours of a Norwegian lemming make it immediately distinguishable from other sympatric rodents, which are brown and grey and flee silently without defence.
Theory suggests that warning signals can evolve by making defended prey distinct from undefended prey. Several traits of the Norwegian lemming fit such an aposematic distinction function. Black and white or yellow is a classic aposematic colouration, avoidance of which does not require learning in some birds.”
If you’re a predator in lemming and vole territory, and one option screams and lunges at you and has colouring that suggests that it maybe tastes disgusting or is poisonous, and the other option is timid, quiet, and of a subtle hue, well, it’s not such a difficult choice. Maybe 'powerful lemming, weak vole’ is the assumption the Norwegian lemming is banking on. Just look into those beady black eyes and tell me it's not banking on something. Exactly.
** Thanks to kgleditsch on Flickr for the lemming images. You can see them here.
Video © Alexander Rydén, who filmed the lemming defence response.